Studies were conducted to determine the capacity of water hyacinth (Eichhornia crassipes [Mart] solms) for uptake of organic and inorganic nutrients from pig slurry because the water hyacinth is considered the species with the highest biomass production capacity, and due to its high nutrient content and heavy metals absorption, it was used for the tertiary depuration of pig slurry. Results showed that a wastewater treatment system using water hyacinth was capable of reducing COD by 100% (60% of reduction to the water hyacinth) when the effluent had up to 1000 mg/1 COD. Significant relationships were observed between the depuration rate and climatic factors (temperature, solar radiation, humidity, etc.). For the months of maximum production of biomass, from June to September, which coincided with the optimum climate, the extent of removal of COD above mentioned was obtained in 8 to 10 days, whereas in the remaining months it required much more time. Inorganic nitrogen (NH4-N and NO3-N) was removed by the water hyacinth the ammonium nitrogen (NH4-N) of the wastewater was reduced by 88% from June t o September, but i n t h e other months ammonium only decreased by 75%, however, only 60% of the nitrate nitrogen was removed. Copyright © 1995 Taylor & Francis Group, LLC. All rights reserved.